import sys

import pygame

from bullet import Bullet
from alien import Alien

def check_keydown_events(event,ai_settings,screen,ship,bullets):
    """响应按键"""
    if event.key == pygame.K_RIGHT:
        #飞船向右左移动
        ship.moving_right = True
    elif event.key == pygame.K_LEFT:
        ship.moving_left = True
    elif event.key == pygame.K_SPACE:
        fire_bullet(ai_settings,screen,ship,bullets)
    elif event.key == pygame.K_q:
        sys.exit()
        
def fire_bullet(ai_settings,screen,ship,bullets):
    """如果没有达到限制就再发一个子弹"""
    #创建新子弹，并将其加入到编组bullets中
    if len(bullets) < ai_settings.bullets_allowed:
        new_bullet = Bullet(ai_settings,screen,ship)
        bullets.add(new_bullet)

def check_keyup_events(event,ship):
    if event.key == pygame.K_RIGHT:
        #飞船向右左连续移动
        ship.moving_right = False
    elif event.key == pygame.K_LEFT:
        ship.moving_left = False

def check_events(ai_settings,screen,ship,bullets):
    #监视键盘和鼠标事件
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                sys.exit()
            elif event.type == pygame.KEYDOWN:
                check_keydown_events(event,ai_settings,screen,ship,bullets)
            elif event.type == pygame.KEYUP:
                check_keyup_events(event,ship)
            
def update_screen(ai_settings,screen,ship,aliens,bullets):
    """更新屏幕上的图像，并切换到新的屏幕上"""
    screen.fill(ai_settings.bg_color)

    for bullet in bullets.sprites():
        bullet.draw_bullet()
    
    ship.blitme()
    aliens.draw(screen)
    
    #让最近绘制屏幕可见
    pygame.display.flip()

def update_bullets(bullets):
    """更新子弹位置，并删除已经消失的子弹"""
    #更新子弹的位置
    bullets.update()
    
    #删除已经消失的子弹
    for bullet in bullets.copy():
        if bullet.rect.bottom <= 0:
            bullets.remove(bullet)
            
def get_number_aliens_x(ai_settings,alien_width):
    """计算每行可以融呐多少个外星人"""
    available_space_x = ai_settings.screen_width - 2*alien_width
    number_aliens_x = int(available_space_x/(2*alien_width))
    return number_aliens_x

def get_number_rows(ai_settings,ship_height,alien_height):
    """计算每行可以融呐多少个外星人"""
    available_space_y = (ai_settings.screen_height -
                         (3*alien_height)-ship_height)
    number_rows = int(available_space_y/(2*alien_height))
    return number_rows

def create_alien(ai_settings,screen,aliens,alien_number,row_number):
    """创建一个外星人，并将其放在当前行"""
    alien = Alien(ai_settings,screen)
    alien_width = alien.rect.width
    alien_x = alien_width + 2*alien_width*alien_number
    alien.rect.x = alien.x
    alien.rect.y = alien.rect.height + 2*alien.rect.height*row_number
    aliens.add(alien)    

def create_fleet(ai_settings,screen,ship,aliens):
    """创建外星人群"""
    #创建一个外星人，并计算一行可容纳多少个外星人
    #外星人间距为外星人的长度
    alien = Alien(ai_settings,screen)
    number_aliens_x = get_number_aliens_x(ai_settings,alien.rect.width)
    number_rows = get_number_rows(ai_settings,ship.rect.height,
                                  alien.rect.height)

    #创建第一行外星人
    for row_number in range(number_rows):
        for alien_number in range(number_aliens_x):
        #创建一个外星人并将其加入当前行
            create_alien(ai_settings,screen,aliens,alien_number,row_number)

def update_aliens(aliens):
    """更新外星人群中所有外星人位置"""
    aliens.update()
        


    
    
